The present invention relates to a construction of a cell for an electro-optical display containing an electrochromic material held in two electrode carrying substrates to manifest reversible variations in the light absorption properties upon application of a predetermined voltage to the electrodes.
The present invention relates, more particularly, to the construction of a substrate for use in an electrochromic display device.
An electrochromic material is one in which the color is changed by the application of an electric field or current. See, for example, L. A. Goodman, "Passive Liquid Displays", RCA Report 613258.
There are two types of electrochromic displays (referred to as ECD hereinafter). The first type of ECD includes an inorganic solid film formed on electrodes, which produces color variations due to a change in the capacity. The second type of ECD utilizes an electrically-induced chemical reduction of a colorless liquid to produce a colored, insoluble film on a cathode surface.
In the conventional ECD, two plate shaped substrates are employed, on which electrodes are formed. The two plate shaped substrates are attached to each other by a spacer. Therefore, the fabrication of the ECD is very complicated, and it is very difficult to accurately determine the distance between the two plate shaped substrates.
Accordingly an object of the present invention is to provide an electrochromic display which ensures stable operation.
Another object of the present invention is to provide a novel substrate for use in an electrochromic display device.
Still another object of the present invention is to facilitate the fabrication of the electrochromic display cell.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
To achieve the above objects, pursuant to an embodiment of the present invention, at least one substrate carrying on electrode is dish shaped to accurately determine the distance between the electrodes formed on the two substrates. The two substrates are attached to each other at their periphery, or, the raised portion of the dish shaped substrate.
In a preferred form, grooves or indented portions are formed at the periphery, or, the raised portion of the dish shaped substrate into which conductive material is introduced to facilitate the electrical connection between the dish shaped substrate and the counter substrate, whereby terminals for the dish shaped substrate are formed on the counter substrate. Another groove is formed at the periphery, or, raised portion of the dish shaped substrate, through which an electrolyte is impregnated into a cavity defined by the two substrates.